In U.S. Pat. No. 3,783,813 it has been proposed to provide a thread-cutting mechanism in which an edge of a stitch plate insert or bushing, forming the needle aperture or hole for passage of the needle therethrough, is formed as a stationary cutting blade which cooperates with a second, movable cutting blade. While with such an arrangement a prime objective of such cutters can be achieved, namely cutting of the upper and lower threads, respectively, leaving short thread ends, some disadvantages arise.
The main disadvantage arises due to the special precautions that need to be taken to avoid accidental cutting of the needle thread portion remaining in the needle eye against the edge of the stitch hole. This end also passes through the needle hole and a special groove must be made for this thread end portion since cutting is carried out at the needle or stitch hole of the throat or stitch plate.
Because the insert or bushing forming the needle hole is subject to considerable wear, caused by the needle and the thread passing therethrough, provision of a cutting edge in such bushing or insert tends to increase this wear and leads to frequent replacement of the needle-hole-forming insert in the throat or stitch plate.